Processs for the production of normal paraffins by urea dewaxing of mineral oil distillates

ABSTRACT

In a urea dewaxing process, a powdery adduct, capable of being effectively separated by centrifuging, is formed at a temperature range of from about 20* to 40* C. if particular oil solvent mixtures are employed. Useful solvent mixtures are a C5-C6 hydrocarbon such as isopentane, hexane or benzene plus a higher boiling organic compound such as methylisobutylketone.

United States Patent Kunert et al.

[ Nov. 12, 1974 PROCESSS FOR THE PRODUCTION OF NORMAL PARAFFINS BY UREA DEWAXING OF MINERAL OIL DISTILLATES [75] Inventors: Max Kunert, Neu-Wulmstorf;

. Lothar Sandhack, Rheurdt, both of Germany [73] Assignee: Deutsche Texaco Aktiengesellschaft,

Hamburg, Germany [22] Filed: Apr. 25, 1973 [21] Appl. No.: 354,284

[30] Foreign Application Priority Data Apr 27, 1972 Germany... 2220594 52 us. Cl. 208/25, 260/96.5 c

[51] Int. Cl Cl0g 43/04 [58] Field of Search 208/25; 260/965 R, 96.5 C

[56] References Cited UNITED STATES PATENTS 3,163,632 12/1964 Leas et al. 208/25 3.600297 8/1971 Franz et a] v. 208/25 FOREIGN PATENTS OR APPLICATIONS 1.105.090 4/1959 Germany 208/25 1225328 9/1966 Germany 260/965 C Primary E.\'aminerHerbert Levine Attorney, Agent, or FirmThomas H. Whaley; C. G. Ries [57] ABSTRACT In a urea dewaxing process. a powdery adduct, capable of being effectively separated by centrifuging, is formed at a temperature range of from about 20 to 40C. if particular oil solvent mixtures are employed. Useful solvent mixtures are a C C hydrocarbon such as isopentane, hexane or benzene plus a higher boiling organic compound such as methylisobutylketone.

7 Claims, N0 Drawings PROCESSS FOR THE PRODUCTION OF NORMAL PARAFFINS BY UREA DEWAXING OF MINERAL OIL DISTILLATES fins from mineral oil distillates by a processknown as urea dewaxing.

It is known to react the n-paraffins components of liquid hydrocarbon mixtures, such as mineral oil distillates, with urea to form solid adducts. These adducts are separated from the mineral oil filtrate by filtration, centrifugation, etc., washed with a solvent for hydrocarbons and, finally, decomposed under the influence of heat, water and/or solvents, thereby recovering the urea and obtaining an n-paraffin product which still contains a minor amount of isoparaffins and other constituents, depending on the mineral oil distillate used and the operating conditions employed. A second product obtained from the mineral oil filtrate by way of this so-called urea dewaxing process is a hydrocarbon mixture which, as a result of the reduced n-paraffin content, has a lower pour point than the charge material.

This urea dewaxing process may becarried out with crystalline urea, advantageously admixed with minor amounts of such materials as water and methanol as an activator. However, aqueous or alcoholic urea solutions' may also be used in this process. The adduct formation is normally carried out at a temperature of from about to 40C, using aqueous urea solutions saturated at an elevated temperature, for example, about 70C.

It is also known that the selectivity of the urea dewaxing process may be,improved by diluting the mineral oil distillate with oil solvents; Suitable oil solvents include low moleculear weight alcohols and ketones, low boiling hydrocarbons such as butane, pentane, isopentane,

hexane, and the like, and halogenated hydrocarbons such as dichloromethane.

German patent no. 1,098,657 discloses a process by which the n-paraffin-urea adduct is obtained as a dustlike powder having a medium particle size of or below about 0.1 mm, in the form of fine to coarse particles or as a very viscous aqueous slurry. The form of the adduct depends, among other factors, on the type of urea solvent used, if one is used, as well as on the concentration and amount of the urea solution; further, on the type of oil solvent used for diluting the mineral oil and, last but not least, on the adduct-forming temperature. Upon decomposition, the dust-like adduct, hereinafter called powder adduct, yields a very pure n-paraffin.

However, this powder adduct cannotbe separatedfrom 1 the mineral oil filtrate by screening. On the other hand,

although a coarse-grained adduct is readily siftable, it cannot be purified sufficiently by washing withzthe oil solvent and so the coarse-grained adduct yields aparaffin product with lower n-paraffin content. German patent no. 1,105,090 discloses a process wherein in a-first stage a coarse-grained adduct is produced, and in a second stage this adduct is stirred with a suitable oilsolvent and cooled to form powder adduct. The second stage employs what is termed a repulping operation.

German patent no. 1,098,657 discloses the influence of the adduct-forming temperature on the form of the adduct; powder adduct is stable only below a defined temperature limit depending, among other factors, on the type of oil solvent used. If, for example, 100 parts by volume of a mineral oil boiling in the range of from 307 to 415C are reacted with 100 parts by volume of aqueous urea solution saturated at C., 300 parts by volume of dichloromethane (DCM) as oil solvent, powder adduct is obtained if the adduct-forming temperature is below 27C.

If, insteadof DCM, hexane or isopentane isused in the same parts by volume, a temperature of below 8C is required to obtain powder adduct. If these solvents are replaced by such solvents as methanol, ethanol, acetone, butanone, methyl formate or methyl acetate, a sticky, nonpiimpable adduct is formed when the temperature ranges between 20 and 35C. Powder adduct is obtained only at substantially lower temperatures than with DCM or C -C hydrocarbons. When higher boiling polar materials such as methylisobutylketone, butylacetate, hexanol, or'the like are used as solvents in adduct formation, very viscous emulsions are obtained which can be neither pumped nor filtered. Al-

I though all these solvents .permitted production of powder adduct at very low adduct-forming temperatures, this mode of operation is not economically feasible because of the high cooling costs. While it is possible to produce adduct with DCM as the solvent in a desirable temperature of about 20 to 40C, the continuous separation of the powder adduct from the liquid mixture by centrifuging is almost impossible because of the small difference in density between the DCM solution and the powder adduct.

It is an object of this invention to provide a process for the recovery of n-paraffins from mineral oil distillateswhereby a powdery adduct is formed at a commercially attractive temperature through use of a solvent which also permits the effective separation of the adduct from the solvent-mineral oil mixture by means of centrifuging.

SUMMARY OF THE INVENTION An adduct in powdery form is formed in a urea dewaxing process at a temperature range of about 20 to 40C. by admixing with the n-paraffin-containing mineral oil distillate an organic solvent of 70 to volume percent of a C C hydrocarbon and 30 to 5 percent of ahigher boiling-organic compound such as methylisobutylketone. The solvent combination has the concomitant. advantage of permitting the effective separation of the powdery. adduct fromthe distillate-solvent mixture by centrifuging.

DESCRIPTIONOF THE PREFERRED EMBODIMENTS We-havefound-that powder adduct is obtainedina urea dewaxing process at an economically and commercially attractive temperature range of from about 20 to 40C., if 70 to 95 volume percent of a C -C hydrocarbon such as isopentane, hexane or benzene and ingly, the separation of the powder adduct from the mineral oil raffinate (primary filtrate), the washing of the adduct with liquid solvent, and also the treatment of the washed adduct, particularly with vaporous solvent, can be effected in a commercial separator such as Therefore, a particularly advantageous and preferred embodiment of the process of the invention is to conduct the reaction at a temperature of between about 20 and 40C and prepare n-paraffin-urea powder ad a full jacket centrifuge. 5 duct having an average particle size of about 0.1 mm

I or less. The present mvemlon, therefore relates to lmprovg' This invention is further illustrated by the following ments in a process for the recovery of n-paraffins from examples. mineral oil distillates comprising reacting the mineral oil, diluted with an organic solvent, with an aqueous or l EXAMPLE I alcoholic urea solution saturated at elevated tempera- A light gas oil boiling in range of from about ture to form solid n-paraffin-urea adducts, separating to (Corresponding to a Carbon number in the the adducts from the dewaxed mineral oil solution, "i of about 12 to 22 d containing about 1 wt. Washlog the adducts Wlth ah orgahlo solvent and percent of n-paraffins was used. 100 parts by volume of eorhposlhg the Washed adducts y orgarlle Solvent 15 this gas oil were diluted with 220 parts by volume of a traetloh or y the lhtlueoee of heat, Water and/ or Said solvent or solvent mixture and then reacted, while stirorganic solvent. The specific improvements of this inring parts olume of an aqueous urea oluvention are directed to diluting the mineral oil distillate tion, Saturated at 70C to f a Solid adduct Charge material a SOiVent mixture Of frOm about. Preliminary test runs were arried out under these 95 to 70 volume percent of hydrocarbons having from conditions to determine the upper temperature limit about 5 to 6 Carbon atoms and of from about 5 to 30 for formation of the adduct in powder form (with an Percent of a higher bolllrlg organic compound Such average particle size of about 0.1 mm or less). The admethyllsobutylketohe lt has further been duct formation was conducted up to or close to this found that miXtufeS of from about 95 to Particularly upper temperature limit. The powder adduct obtained about 90 to Volume Percent of allphatle, eyeloall" was separated from the liquid by filtration. Then, it was Phatle or aromatic s s hydrooarbons, for example, washed at adduct-forming temperature, using the same lsopehtahe, hexane or benZene, and from about5 to 30, type and same amount of solvent or solvent mixture Preferably about 10 to 20, volume percent of MlBK, employed in the adduct-forming step. Finally, the powused as oil Solvents for the Prorluetloh of -P der adduct, washed and largely freed of the wash agent, urea adducts, are not y Capable of ralslhg the was decomposed under addition of hot water. The re- Perature llmlts for Powder adduct formation to the sults are set forth in Table 1 below. The expression ncorhrherelally attraetlve temperature range of about paraffin yield in the Table designates the content by 20 to C, but they are also excellent wash agents, so i h f f i b d on Charge material, efficient in freeing powder adduct and also fine-grained mi upon decomposition of the powder addu The to coarse-grained n-paraffin-urea adducts from isopar- 5 expression i f ffi designates the afflos and other eohstltuerlts y Washlhg, P P portion of n-paraffins in the decomposition product. tion and the like, that y P normal ParaffihS are In comparative Runs 1 to 4, the gas oil was diluted obtained upon decomposition of the adducts having i h hexane, benzene, isopomano or mothyiisobw been treate d therewith tylketone (MIBK). In Runs 1 to 3, powder adduct was Oil solvent mixtures consisting of from 95 to 70 vol- 40 formed only up to the upper temperature limit indiume percent of C or C hydrocarbons and from 5 to cated in Table I. At higher adduct-forming tempera- 30 volume percent of MIBK, are also suited to modify tures, a coarse-grained or greasy, sticky adduct slurry the so-called repulping process known from German was obtained. When MIBK was used as diluent (Run patent no. 1,105,090 so as to produce powder adduct 4), a non-filtrable adduct gel was formed, both at room at the economically feasible temperature range emtemperature and at lower temperatures. For this reaployed in the first stage. This powder adduct can then son, the n-paraffin yield and purity could not be deterbe washed (with the same fresh oil solvent mixture) mined. and, finally, dispersed (repulped) therein with stir- In Runs 5 to 8, the first solvent, i.e., hexane (Runs 5 ring. As distinct from the procedure disclosed in Gerand 6) or benzene (Runs 7 and 8), was admixed with man patent no. l,l05,090, this dispersion can be MIBK in amounts of about 5 and 10 volume percent heated to a temperature substantially above the ad- (based on said first solvent), respectively. As shown in duct-forming temperature, without thereby causing the Table I, the temperature limits for the formation of the adduct to conglomerate or cake. If these dispersions desired adduct were thereby raised quite considerably. are, subsequently, recooled to the original adduct- Furthermore, there was a distinct increase in yield and forming temperature, very pure n-paraffins in fairly purity of the n-paraffms obtained as compared with high yields are obtained from the adduct. comparative Runs 1 to 3.

TABLE I RUN NO. 1 2 3 4 5 6 Gas oil, parts by volume I00 I00 I00 I00 I00 I00 Aqueous urea sol. (70C saturation), parts by volume 60 60 60 60 60 Is! solvent, hexane benzene isopcntane MIBK hexane hcxunc parts by volume 220 220 220 220 210 200 RUN NO. 1 2 3 4 5 6 2nd solvent, MIBK MIBK parts by volume Upper temperature limit, powder adduct. C 4 +3 6 53 Adduct-forming temperature, C 4 0 6 25 25 25 n-Paraffin yield, wt.% 15.2 18.9 17.7 15.9 16.1 Purity of n-paraffin, wt.% 91.5 92.0 90.0 94.7 95.0

Run No. 7 8 Gas oil, parts by volume 100 100 Aqueous urea sol. (70C saturation),- parts by volume 60 60 1st solvent, benzene benzene parts by volume 210 200 2nd solvent, MIBK MIBK parts by volume 10 20 Upper temperature limit, powder adduct, C 32 61 Adductforming temperature, C 25 25 n-Paraffin yield, wt.% 19.3 19.6 Purity of n-paraffin,

Notes: non-filtcrable gel EXAMPLE lI A-spindle oil 0 boiling in the range of from about 317 to 420C (corresponding to a carbon number range of between about 14 and 28) and containing about 16 wt. percent of n-paraffins was used. 100 parts by volume of said spindle oil were diluted with 200 parts by volume of an oil solvent or solvent mixture and reacted at temperatures of 20 or C with parts by volume of an aqueous urea solution, saturated at C. The results are set forth in Table II below.

Comparative Runs 9, 10 and 13 were conducted with pure hexane as solvent and with an adduct-forming temperature of 20C. A fine-grained adduct (average particle size 0.1 to 0.3 mm) resulted. In comparative Runs 15, 16 and 19 an adduct having a particle size of from about 0.3 to 0.6 mm was formed at 35C. Powder adduct (average particle size about 0.1 or less) was obtained only at a temperature of 8C or lower. At higher adduct-forming temperatures, and with hexane as solvent, a sticky adduct was obtained, which showed no further reaction. In Runs 11, 12, 14, 17, 18 and 20, MIBK was substituted for about 5 volume percent of said hexane. By doing this and maintaining the other conditions, the av erage particle size of the adduct was reduced to 0.1 mm or less. The n-paraffins obtained from the runs using MIBK as a diluent component were of greater purity than those obtained in the comparative runs using hexane.

45 spindle oil charge) of the oil solvent or solvent mixture,

stirred at the adduct-forming temperature employed for 5 min, filtered and again washed with the same amount of the same fresh solvent or solvent mixture. As the increase in purity of the recovered n-paraffins 50 shows the addition of MIBK was also advantageous in this repulping treatment.

The data of Runs 9 to 20 are summarized in the following Table II.

TABLE II RUN NO. 9 10 ll 12 l3 l4 Spindle oil 0, parts by volume 100 100 100 100 100 Urea sol., 70C sat. parts by volume 50 50 50 50 50 50 1st solvent, Hexane Hexane Hexane Hexane Hcxanc Hexune parts by volume 200 200 190 200 190 2nd solvent MIBK MIBK MIBK parts by volume 10 10 10 Adduct-form. temp.. C 20 20 20 20 20 20 Adduct particle size, mrn. 0.1-0.3 0.1-0.3 0.1 0.1 0.1-0.3 0.1 1st wash solvent, Hexane Hexane Hexane Hexane Hexane Hexane parts by volume TABLE II Continued RUN NO. 9 10 11 12 13 14 2nd wash solvent MIBK MIBK MIBK parts by volume l0 l0 l0 Repulping temp, "C 20 20 Repulping time, min 5 5 lst repulping solvent, Hexane Hexane parts by volume 200 I90 2nd rcpulping solvent. MIBK parts by volume l0 n-Paraffin yield, wt.% 17.6 16.8 16.2 16.3 15.9 1507 Purity of n-puraffin, wt.% 87.0 92.0 93.5 94.5 95.0 96.5 011 content (ASTM) wur 19.3 11.1 10.0 8.5 4.8 39 Run No. 15 10 17 111 19 20 Spindle oil 0. parts by volume 100 l00 I00 I00 I00 I00 Urea sol, 70C 52"., parts by volume 50 50 50 50 50 50 lst solvent, Hexane Hexane Hexane Hexune Hexane Hexanc parts by volume 200 200 190 I90 200 190 2nd solvent. MIBK MIBK MIBK parts by volume l0 l0 l0 Adduct-form. temp, C 35 35 35 35 35 Adduct particle size, mm. 0.3-0.6 0.3-0.6 01 0.1 0.3-0.6 0.1 ls! wash solvent, Hexane Hexane Hexane Hexane Hexane Hexane parts by volume 200 190 200 I90 200 190 2nd wash solvent, MIBK MIBK MlBK parts by volume l0 l0 l0 Repulping temp, C 5 5 lst rcpulping solvent. Hcxane Hexane parts by volume 200 190 2nd repulping solvent MIBK parts by volume l0 n-Paraffin yield. wt.% 17.8 17.1 16 5 16.0 l6.l 15.6 Purity of n-paraffin, wt.% 85.0 89.0 92 0 93.3 94.4 963 Oil content (ASTM), wt.% 14 5 12.2 8 2 7.4 4.5 3.2

We claim: 35 2. A process according to claim 1 wherein the vol- In a Process for the recover) of n'parafflns from ume percent of C -C hydrocarbon is 80 to 90 volume mineral oil distillates comprising reacting the mineral percent d h volume percent f h r h oil, diluted with an organic solvent, at a temperature of ik r i 20 to 10 volume percent 20 to 40C, with an aqueous or alcoholic urea solution 3, A process according to Ciaim 1 wherein the CYC" saturated at elevated temperature to form solid n- 40 i isoperitaho paraffin-urea adducts, separating the adducts from the 4, A process according to l i 1 h i the CFC6 dewaxed mineral oil solution, washing the adducts with hyd b i hexans an organic solvent and decomposing the washed ad- 5. A process according to claim 1 wherein the C ,C ducts by organic solvent extraction or by the influence h d b i horizons of heat, Water and/0 a rg m Solvent, the pro 6. A process according to claim 1 wherein a powdery ment which comprises diluting the mineral Oll distillate adduct having an average particle size of 0.1 mm. or charge material in the adduct-forming step with an orl i f d i h dd f i step. ganic solvent which is a solvent mixture consisting es- 7. A process according to claim 1 wherein the solvent sentially of from about 70 to 95 volume percent of a mixture is employed as the organic solvent to wash the C -C hydrocarbon and of from about 30 to 5 volume adduct and to decompose the adduct. percent of methylisobutylketone. =1 1 

1. IN A PROCESS FOR THE RECOVERY OF N-PARAFFINS FROM MINERAL OIL DISTILLATE COMPRISING REACTING THE MINERAL OIL, DILUTED WITH AN ORGANIC SOLVENT, AT A TEMPERATURE OF 20* TO 40*C, WITH AN AQUEOUS OR ALCOHOLIC UREA SOLUTION SATURATED AT ELEVATED TEMPERATURE TO FORM SOLID N-PARAFFIN UREA ADDUCTS, SEPARATING THE ADDUCTS FROM THE DEWAXED MINERAL OIL SOLUTION, WASHING THE ADDUCTS WITH AN ORGANIC SOLVENT AND DECOMPOSING THE WASHED ADDUCTS BY ORGANIC SOLVENT EXTRACTION OR BY THE INFLUENCE OF HEAT, WATER AND/OR SAID ORGANIC SOLVENT, THE IMPROVEMENT WHICH COMPRISES DILUTING THE MINERAL OIL DISTILLATE CHARGE MATERIAL IN THE ADDUCT-FORMING STEP WITH AN ORGANIC SOLVENT WHICH IS A SOLVENT MIXTURE CONSISTING ESSENTIALLY OF FROM ABOUT 70 TO 95 VOLUME PERCENT OF A C5-C6 HYDROCARBON AND OF FROM ABOUT 30 TO 5 VOLUME PERCENT OF METHYLISOBUTYLKETONE.
 2. A process according to claim 1 wherein the volume percent of C5-C6 hydrocarbon is 80 to 90 volume percent and the volume percent of the methylisobutylketone is 20 to 10 volume percent.
 3. A process according to claim 1 wherein the C5-C6 is isopentane.
 4. A process according to claim 1 wherein the C5-C6 hydrocarbon is hexane.
 5. A process according to claim 1 wherein the C5-C6 hydrocarbon is benzene.
 6. A process according to claim 1 wherein a powdery adduct having an average particle size of 0.1 mm. or less is formed in the adduct forming step.
 7. A process according to claim 1 wherein the solvent mixture is employed as the organic solvent to wash the adduct and to decompose the adduct. 